<button onclick="show()">show</button>
<button onclick="hide()">hide</button>
<script>
//创建加载对象
var obj = new loadingImg();
//显示加载图片
function show(){
  obj.show();
}
//隐藏加载图片
function hide(){
  obj.hide();
}
//加载图片方法（对象）
function loadingImg(mySetting){
  var that = this;
  if(mySetting == "" || mySetting == undefined || typeof mySetting != "object"){
    mySetting = {};
  }
  //使用时间戳作为空间的ID
  var targetID = new Date().getTime();
  this.setting = {
    //插入图片的容器,使用jquery的查询方式传入参数
    targetConater : "",
    //使用图片的地址
    imgUrl : "../img/loading.gif",
    //图片显示的 宽度
    imgWidth : "32px",
    //图片的默认样式
    imgClass : "",
    //生成控件的ID
    "targetID" : targetID,
    //显示之前的回调函数
    beforeShow : function(plugin){
    },
    //显示之后的回调函数
    afterShow : function(plugin,targetID){
    }
  }
  this.setting = $.extend(this.setting, mySetting);
  //获取屏幕的宽度
  this.getScreenWidth = function(){
    return document.documentElement.clientWidth;
  }
  //获取屏幕的高度
  this.getScreenHeight = function (){
    return document.documentElement.clientHeight;
  }
  //显示控件
  this.show = function(){
    $("#" + that.setting.targetID).show();
  }
  //隐藏控件
  this.hide = function(){
    $("#" + that.setting.targetID).hide();
  }
  this.init = function(){
    //显示之前执行回调函数
    if(typeof that.setting.beforeShow == "function"){
      that.setting.beforeShow(that);
    }
    //存放字符串的变量
    var targetHTML = '';
    //将内容存放到指定的容器中，默认存放到body最底部
    if(that.setting.targetConater != "" && this.setting.targetConater != undefined){
      targetHTML = '<img src="' + that.setting.imgUrl + '" class="' + that.setting.imgClass + '" id="' + that.setting.targetID + '" style="display:none;">';
      $(that.setting.targetConater).html(targetHTML);
    }else{
      targetHTML = '<img src="' + that.setting.imgUrl + '" class="' + that.setting.imgClass + '">';
      targetHTML = '<div id="' + that.setting.targetID + '" style="display:none;position: absolute;top:50%;left: 50%;height: ' + that.getScreenHeight()+';width:'+that.getScreenWidth()+'">' + targetHTML + '</div>';
      $("body").append(targetHTML);
    }
    //判断用户是否自定义了图片的宽度
    if(that.setting.imgWidth != "" && that.setting.imgWidth.indexOf("px")>0 ){
      $("#"+targetID).css("width",that.setting.imgWidth);
    }
    //显示之后执行回调函数
    if(typeof that.setting.afterShow == "function"){
      that.setting.afterShow(that,targetID);
    }
  }
  this.init();
}
</script>